1. Field of the Invention
The present invention relates generally to a control circuit, and more particularly to a control circuit being used for identifying an adaptor used with an electronic device when the adaptor is used to power the electronic device. The present invention also relates to a method for identifying adaptors.
2. Description of Related Art
As our world becomes more technologically advanced, the demand for electrical power becomes more sophisticated. With the advent of portable electronic devices, such as notebook computers, mobile telephones, personal digital assistants (PDAs), digital still/dynamic cameras, etc, there is increasing demand for increased electrical power supply duration for these electronic devices.
Conventionally, these portable electronic devices rely on batteries or are electrically connected to an AC/DC power adaptor to get power. Referring to FIG. 5, a power adaptor according to related art is shown to generally include a step-down circuit 10 and a rectifier circuit 20. The step-down circuit 10 receives an external high alternating current voltage from an AC voltage source (not shown) and converts the received high alternating current voltage to a low alternating current voltage. The rectifier circuit 20 then converts the low alternating current voltage into a low direct current voltage that is outputted through positive and negative output terminals 1+, 2− to power a system that is connected to the adaptor, wherein the system may be an electronic device such as a notebook computer.
Adaptors are now in widespread use in electronic products, especially in the computer field. The power adaptor mentioned in FIG. 5 adopts a universal design and thus lacks the ability to identify between different electronic devices that are produced by different vendors. If the power adaptor is not the original vendor's product, it may cause some negative effects. For example, bogus adaptors cause damage to the original vendor, both in profit and the brand. Incompatible or bogus adaptors have influence on the safety and stability performance of computers, and the life thereof will be significantly shortened as a result.
It is therefore desirable to provide a control circuit capable of identifying an adaptor used with an electronic device, which can overcome the above mentioned problems.